More than half of the S&P 500 companies have reported third-quarter financial results so far, and while more than 70% have delivered earnings above Wall Street's estimates, only 36% have topped sales forecasts, according to FactSet Research. That is well below the average of 55% that typically beat revenue estimates.

Moreover, companies have been tepid in their outlooks for the remainder of the year.

The dull results have pushed investors to the sidelines. In fact, all three indexes posted their second weekly loss in three weeks. The Dow Jones industrial average declined 1.8%, the S&P 500 slid 1.5%, and the Nasdaq dropped 0.6% during the week.

In addition, traders have become risk-averse ahead of the U.S. presidential elections, while concerns about the fiscal cliff continue to weigh on the market. The uncertainty has stocks on track to finish October in the red, logging their first monthly loss since May.

Trading on Friday was choppy, as investors remained focused on earnings but also digested a mixed bag of economic data.

A stronger-than-expected report on U.S. economic growth was encouraging, but a reading on consumer sentiment fell short of expectations.

Gross domestic product, the broadest measure of economic activity, rose at a 2% annual rate in the third quarter, according to government data. The figure was higher than the 1.7% rate economists surveyed by CNNMoney had forecast. GDP grew at a rate of 1.3% in the second quarter.

While the University of Michigan's index measuring consumer sentiment improved in October to 82.6 from the prior month, it was revised down from a preliminary reading of 83.1, disappointing analysts who were expecting the index to remain unchanged

After flipping between small gains and losses through the trading day, the Dow and Nasdaq finished up less than 0.1%, while the S&P 500 shed 0.1%.

Banks were among the biggest decliners, with Bank of America(BAC) and JPMorgan Chase(JPM) dragging on the Dow. Citigroup(C) shares fell sharply after Massachusetts regulators fined one of the bank's unit $2 million for failing to prevent analysts from illegally leaking confidential information about Facebook's(FB) initial public offering.

Companies:Apple(AAPL), one of the most widely held stocks in the S&P 500, reported quarterly results that missed expectations, as iPad sales came in lower than forecasts. But the company's forecast for next quarter was a blockbuster, as Apple said it expects sales of around $52 billion, up 12% from last year's holiday quarter. Shares of Apple slipped almost 1% Friday.

Amazon(AMZN) shares rose 7% a day after the company reported a narrower-than-expected loss, despite missing on sales.